teonina tubulata (= Saccammina sphaerica),Pyrgo williamsoni, Trocha mmina intermedia(= T. ochracea), Uvigerina angulosa(=Trifarina angulosa), and Webbinellahemisphaerica (= Hemisphaerammina bradyz),were collected in large quantities from the cliffhabitat. The variation in the foraminiferal abun-dances between cliffs and mud may be attributedto their displacement from a favorable into anunfavorable habitat.

Many foraminifera found off the AntarcticPeninsula have been encountered by workers whohave studied foraminifera off South America.Lena (1966) noticed that the littoralforaminiferal fauna off the tip of South Americais Subantarctic in nature but biogeographicallybelongs to the Argentinean province. Suchstudies must be noted because of the relativelyclose proximity of South America to the Antarc-tic Peninsula. Since the Early Tertiary the ScotiaArc has served as a connection between these twocontinents (Adie, 1963) and as a migration routefor benthic organisms (Dell, 1972). Out of 69species encountered by Lena, 15 occurred in theArthur Harbor area. These included Cassidulina(= Globocassidulina) crassa, Cassidulinoidesparkerianus, Cornuspira (= Cyclogyra) invol-vens, Epistominella (= Pseudoparrella) exigua,Fissurina earlandi, F. laevigata, Hemisphaeram-mina bradyi, Hippocrepinella alba, Nodosariacalomorpha, Ovammina sp., Patellinacorrugata, Pullenia su bcarinata, Quin-queloculina seminulum, Saccammina decorata,and Spiroplectammina bformis.

Echols, R.J., and J.P. Kennett. 1973. Distribution offoraminifera in surface sediments. Antarctic Map FolioSeries, 17. New York, American Geographical Society.

Everson, I., and M.G. White. 1969. Antarctic marinebiological research methods involving diving. In: Under-water Association Report 1060 (Lythgoe, J.N., editor).91-95. Surrey, England. Life Science and Technology.

Hulings, Neil C., and J.S. Gray. 1971. A manual for thestudy of meiofauna. Smithsonian Contributions toZoology, 78. Washington, D.C., Smithsonian InstitutionPress.

Lena, H. 1966. Foraminiferes recientes de Ushuaia (Tierradel Fuego, Argentina). Ameghiniana, 4: 311-336.

Stockton, W.L. 1973. Distribution of benthic foraminiferaat Arthur Harbor, Anvers Island. AntarcticJournal of theU.S., VIII(6):348-350.

Intertidal region and molluscanfauna of Seymour Island,

Antarctic Peninsula

WILLIAMJ. ZINSMEISTERInstitute of Polar StudiesThe Ohio State University

Columbus, Ohio 43210

I am grateful to my colleagues T. DeLaca, K.Finger, A.P. Giannini, Jr, T.A. Kauffman,W.N. Krebs, G. Zumwalt, and especially to mywinter companions T. Brand and R. Moe, fortheir assistance. I thank Dr. Lipps, Departmentof Geology, University of California, Davis, forsupport and guidance. This paper is a summaryof my thesis submitted in partial fulfillment ofthe requirements for the M.S. degree in ecologyat the University of California, Davis.

References

Adie, R.J. 1963. Geological evidence on possible antarcticland connections. In: Pacific Basin Biogeography(Gressitt, J . L., editor). 455-463. Honolulu.

DeLaca, T.E., andJ.H. Lipps. 1976. Shallow-water marineassociations, Antarctic Peninsula. Antarctic Journal ofthe U.S., XI(1): 12-20.

Dell, R.K. 1972. Antarctic benthos. Advances in MarineBiology, 10: 1-216.

During the 1974-1975 austral summer a jointgeological field party from Instituto AntárticoArgentino and Ohio State University spent 5weeks studying the Late Cretaceous to Early Ter-tiary stratigraphy and paleontology of the northend of Seymour Island (Elliot et al., 1975). Muchtime was spent examining outcrops exposedalong the sea cliffs. During low tides I observedand collected molluscs from the intertidal region.This brief note describes the intertidal zone andits molluscan fauna along the north coasts ofSeymour Island.

Seymour Island is southeast of the north end ofthe Antarctic Peninsula (figure 1). Ice conditionsare unpredictable because of the island's locationon the edge of the Weddell Sea. During the1974-1975 spring and summer the prevailingsoutheast winds drove the sea ice northwardalong the east coast of the Peninsula. Most of theice passes along the east coast of Seymour Islandwith lesser amounts of pack ice passing to thewest through Admiralty Sound. Shallow depths

222 ANTARCTIC JOURNAL

in waters around Seymour Island cause all largeicebergs to be grounded well offshore. Stronglongshore currents flow northward along the eastcoast. These currents swing to the northwest asthey pass Cape Wiman at the north tip of theisland. Sand and silt eroded from the sea cliffsare transported by these currents along the shoreand are eventually deposited in a large spit atLarsen Cove, near the northern tip of the island(figure 2).

The intertidal region of Seymour Island isunique for the Antarctic. It varies from narrowboulder beaches to broad mudflats and sandspits. The type of beach and intertidal zonedepends on the degree of exposure to storms andon the movement of ice and currents from theWeddell Sea. The lithology of rocks from the seacliffs has special importance. The rocks generallyconsist of loosely consolidated sandstones and sil-ty clays with local conglomeratic lenses and in-terbedded horizons with resistant concretions.The loosely consolidated nature of the rocks leadsto exceptionally rapid erosion of the sea cliffs.

The intertidal region of Seymour Island maybe divided into two basic types. On the exposedeast coast, the beaches are narrow and consist ofboulders and sand. On the protected west side ofthe island, north of Bodman Point, the intertidalregion is characterized by broad mudflats (figure3).

Exposed coast. The intertidal region along theexposed coastal areas varies from coarse, rockybeaches to narrow, sandy beaches backed bywave-eroded cliffs. The height of the cliffs alongthe east coast varies from 0 to 100 meters. Theswash zone extending to the base of the sea cliff isgenerally composed of very coarse gravels that ex-tend to the mid low-tide zone. The sediment ofthe intertidal region below the mid low-tide zonedepends on the lithology of the sea cliffs.

Beaches along regions where concretions arecommon in the cliffs are quite rocky (figure 4). Incontrast, in areas where concretions are rare thebeaches are generally sandy with minor amountsof small pebbles (figure 5). Ice erosion along theeast coast appears to be minimal. No microrelieffeatures (i.e., ice-push ridges) associated with ac-tive ice movement were observed. During thesummer, brash ice drifts with the longshore cur-rents and is grounded quietly at low tide. Thepassive movement of the brash ice can be at-tributed largely to the damping effect of largeicebergs grounding offshore.

Protected coast. In contrast, the west coast ofSeymour Island north of Bodman Point ischaracterized by a broad, shallow, protected bay

Figure 1. Location maps for Seymour Island area.

with extensive mudflats (figure 6). Strong cur-rents that flow through Admiralty Sound arekept well offshore by Bodman Point. Almost allthe sand and mud carried by the streams of CrossValley and derived from the sea cliffs is depositedon the immediate beach of this bay and forms abroad mudflat 300 to 400 meters in width. Thereis no evidence of any ice abrasion anywhere in thebay, except for a shallow kettle-like depression

X117M,

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Figure 2. Large sand spit on the east side of Larsen Cove.

December 1976 223

Figure 3. Distribution of intertidal along the northeast coastof Seymour Island.

along the beach where brash ice has been strand-ed (figure 7). The only relief on the mudflats con-sists of shallow and meandering tidal channelsand of low rock mounds. These mounds appearto be erosional remnants of concretionaryhorizons that have survived, whereas the looselyconsolidated sediments have been removed byerosion. The shore along Larsen Cove near thenortheast tip of the island is also characterized bybroad and protected mudflats.

Intertidal molluscan fauna. The intertidalfauna of Seymour Island is unusual for Antarc-

tica. The macrofauna is characterized by fourspecies of mollusks (Yoldia eightsi, Laternulaellipitica, Pat inigera polaris, and A mauropsisaureolutea) along with large numbers of speciesof amphipods, isopods, and annelids. The largeisopod Serolis, previously recorded only from thesublittoral zone of Antarctica, is also an impor-tant element of the intertidal fauna. Red andgreen algae occur as large masses on the mudflatsand in amongst the boulders on rocky beaches.Diatom colonies typically cover rocky surfaceswith slimy, fur-like growth.

Two species of mollusks (Yoldia ezghtsi andA mauropsis aureolutea) appear to be restrictedto the protected mudflats north of BodmanPoint. Neither of these species of mollusks hasbeen reported before from the intertidal zone,although this may be because little is knownabout the distribution and ecology of most Ant-arctic mollusks. Powell's survey (1960) of antarc-tic and subantarctic mollusks lists both species asbeing sublittoral. DeLaca and Lipps (1976)reported that Y. eightsi is a common member ofthe subtidal, soft, muddy substrate fauna fromAnvers Island. Its occurrence on the intertidalmudflats of Seymour Island indicates that bothspecies range into the intertidal region providedthat the proper substrate is present.

Numerous disarticulated valves of the fragilebivalve Laternula ellipitica were found as beachwash on both exposed and protected coasts.Because no live individuals of L. ellipitica weretaken, it is not known whether this species actual-ly lives in the intertidal region. Studies aroundAnvers Island indicate that the motion ofgrounded ice frequently dislodges L. ellipitica(Kauffman, 1974). Once this feeble, burrowingbivalve is removed from the soft muddy substrateit generally falls prey to predators (Lipps, per-

Figure A. Rock beach on exposed east coast of SeymourFigure 5. Sand and grave' beach on exposed east coast.Island.

224 ANTARCTIC JOURNAL

sonal communication). Although the beach-washed valves on Seymour Island may representindividuals from a subtidal population, L.ellipitica—as in the case of Y. eightsi—may ac-tually range into the intertidal region.

The large limpet Patinigera polaris was onlyobserved on the boulder beaches of the exposedeast coast. Many individuals were found on thesides and beneath large boulders. P. polaris ap-pears to be restricted to the most rocky part of thebeach, and it was never observed in areas wheresand occurred in significant amounts between therocks. Migration of P. polaris into deeper waterwould appear to be impossible because of thesand and mud; during the winter freeze,therefore, its survival depends on its ability tomigrate into cracks and crevices in looseboulders. Frequent grounding of tabular icebergsclose to shore tends to dampen any storm-generated waves; as a result, movement of looseboulders on the beach appears to be minimaleven during storms.

Summary. This brief survey suggests that thedistribution of many shallow-water invertebrates,for example Yoldia eightsi and Amauropsisaureolutea, depends on the occurrence of asuitable substrate. The extensive intertidalmudflats along the west coast of Seymour Islandoffer a unique opportunity for the study of thedistribution and ecology of shallow-water marineinvertebrates of Antarctica.

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4

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Figure 6. Broad mudflat just north of Bodman Point at lowtide.

References

DeLaca, I.E., andJ.H. Lipps. 1976. Shallow-water marineassociations, Antarctic Peninsula. A ntarctic Journal ofthe U.S., XI(1): 12-20.

Elliot, D.H., C. Rinaldi, W.J. Zinsmeister, T.A. Trautman,W.A. Bryant, and R. del Valle. 1975. Geological in-vestigations on Seymour Island, Antarctic Peninsula. An-tarcticJournal of the U.S., X(4): 182-186.

Kauffman, T.A. 1974. Seasonality and disturbance in ben-thic communities, Arthur Harbor, Antarctic Peninsula.AntarcticJournal of the U.S., IX(6): 307-310.

Powell, A.W.B. 1960. Antarctic and subantarctic mollusca.Auckland Institute and Museum Records, 5(3/4):117-193.

I thank David Elliot, Institute of Polar Studies,for his help and advice on both fossil and recentmaterial collected during the 1974-1975 season.Jere Lipps and his students were kind enough toreview this short note and to provide some un-published data from their work at Anvers Island.I also express gratitude to Argentina's DireccionNacional del Antártico and Instituto AntárticoArgentino for their field support. Lastly, I thankRae Mercier, Institute of Polar Studies, for herpreliminary editing of this and many otherpapers that I have written. This research was sup-ported by National Science Foundation grantDPP 74-21509.

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/.-..

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--3,Figure 7. Broad mudflat exposed at low tide at the mouth ofCross Valley. Shallow ponds in foreground result frommelting of stranded brash ice. Dark mounds on the mudflat

are resistant erosional remnants.

December 1976 225